This invention relates to a method and apparatus for producing a photosensitive layer, used for photosensitive films for electrophotography, on a cylindrical conductive substrate by using plasma CVD techniques.
Photosensitive layers, used for photosensitive films for electrophotography employed as electrostatic copiers, printers for computers, etc., have been produced by using, for example, evaporation of selenium, or selenium alloys, coatings of resins containing cadmium sulfide and zinc oxide, or coatings of organic photoconductive materials. However, photosensitive films for electrophotography having a photosensitive layer composed of, for example, an amorphous silicon (hereinafter given by a-Si) having high surface hardness and good heat resisting property have recently attracted as photosensitive materials with long life and high reliability. The photosensitive layers of a-Si have been produced by plasma CVD techniques. The production of such a photosensitive layer has been carried out, for example, by arranging a cylindrical conductive substrate, coaxially supported by a rotatable support, in a reaction chamber, introducing a reaction gas, composed mainly of, for example, monosilane (SiH.sub.4), into the reaction chamber after vacuum exhausting it, keeping the reaction chamber at a desired vacuum degree, heating the cylindrical substrate to a desired temperature, and decomposing the reaction gas by applying a high frequency voltage between the cylindrical substrate and a cylindrical electrode oppositely arranged around the substrate so as to generate a glow discharge therein, thereby depositing a-Si layer on the structure (Referring to T. Kawamura, M. Nakano, et al, Papers of the General Meeting of the Inst. of Electronics and Communication Engineers of Japan, March 1980, pp 2-269-270). Although the photosensitive films for electrophotography have been practically required for large surface area, it is difficult to deposit uniform photosensitive layer on the cylindrical substrate having considerably large diameter and length in order to obtain uniform image or picture thereon.